Advances in the miniaturization of micro-electromechanical systems have led to small form-factor battery-powered sensor nodes that have sensing, communication and processing capabilities. These sensor nodes are often networked in an ad hoc manner to perform distributed sensing and information processing. Wireless sensor networks differ from other ad hoc networks by requiring a deployment phase. In general, deployment is either random or deterministic. In random deployment, sensor nodes are deployed, for example, by air-dropping them or distributing them randomly in a target environment. Using a deterministic scheme, sensors are placed at pre-determined locations.
Protocols for self-configuration of sensor nodes in a randomly-deployed wireless sensor network may not be suited for a deterministically-deployed sensor network. Similarly, node-to-node data dissemination algorithms designed for deterministic wireless sensor networks may not perform well when used in randomly-deployed sensor networks. Once deployed, however, a wireless sensor network needs very little human intervention and can generally function autonomously to provide continuous monitoring and processing capabilities. Each sensor node collects data (e.g., temperature, sound, vibration, pressure, motion, pollutants, etc.) from a monitored area. The sensing area of a sensor node is typically dependent on the type of physical sensors used by the node.
Nodes systematically route sensed data according to preconfigured communication protocols to a remote base station, where parameters characterizing the collected data are utilized for arbitrary purposes. In such scenarios, data transmission is generally node-to-node multi-hop toward the base station. Since sensor nodes are typically powered by batteries, and because route discovery and data transmission are energy-expensive operations, conserving sensor node battery power during route discovery and/or data transmission operations is a significant consideration when assessing the life of the sensor nodes in a wireless sensor network.